MINOR: quic: Add a max window parameter to congestion control algorithms

MINOR: quic: Add a max window parameter to congestion control algorithms

Add a new ->max_cwnd member to bind_conf struct to store the maximum
congestion control window value for each QUIC binding.
Modify the "quic-cc-algo" keyword parsing to add an optional parameter
to its value: the maximum congestion window value between parentheses
as follows:

      ex: quic-cc-algo cubic(10m)

This value must be bounded, greater than 10k and smaller than 1g.